1. Field of the Invention
The present invention relates in general to a method for checking top and end of a tape for data recording and reproducing apparatus and, more particularly, to an improvement in the top-end checking method for making the top-end checking time become optimal and for saving power of the recording and reproducing apparatus, and for reducing the pulse noise generated in turning on and turning off a top-end checking LED.
2. Description of the Prior Art
With reference to FIG. 1, there is shown a general theory for checking tape top and tape end for data recording and reproducing apparatus in accordance with the prior art. As shown in this drawing, when a tape cassette 1 having a top-end LED hole T-EH on the upper center of its bottom surface is loaded on a deck mechanism of the apparatus, a light emitting part 4 which comprises an LED and is provided on the deck mechanism will be aligned with the center of the top-end LED hole T-EH of the cassette 1. The opposite front side surfaces of the cassette 1 are provided with their light windows 3 and 3' for transmitting the light of the light emit part 4 to their associated light receive parts 5 and 5', which parts 5 and 5' are arranged on the deck mechanism so that they face the light windows 3 and 3' of the cassette 1 respectively. The deck mechanism of the data recording and reproducing apparatus further includes a head drum 2 which is placed in front of the loaded cassette 1. The head drum 2 has a head for recording or reproducing data on or from a tape of the cassette 1.
In order to check tape top and tape end through a typical checking method during recording or reproducing data on or from the tape of the cassette 1, the light emit part 4 aligned with the center of the top-end LED hole of the cassette 1 emits the light. When letting the first reel and the second reel of the cassette 1 of FIG. 1 be a tape supply reel and a tape take-up reel respectively, and letting the tape be primarily unwound from the first reel and be wound about the second reel, a first transparent tape section provided on the start portion of the tape appears and passes by the right window 3 of the cassette 1. In this case, the light of the light emit part 4 of the deck mechanism which was introduced into the hole T-EH of the cassette 1 is received by the light receive part 5 of the right side through both the first transparent tape section and the right window 3. However, when the magnetic coated tape section passes by the right window 3 after lapse of a predetermined time, the light of the light emit part 4 will not be transmitted to the light receive part 5 of the right side any more as the light can not be transmitted through the magnetic coated tape section. Thus, the light receive part 5 of the right side will recognize the tape top (i.e., the start of the tape). When the tape of the first reel is completely wound about the second reel, the light receive part 5' of the left side receives the light of the light emit part 4 through both a second transparent tape section provided on the end portion of the tape and the left window 3'. Hence, the light receive part 5' of the left side will recognize the tape end. When the tape runs in the reversed direction such as in a REWIND mode of the deck mechanism, the light receive part 5' of the left side will recognize the tape top, while the light receive part 5 of the right side will recognize the tape end.
However the above tape top and tape end checking method has a problem. That is, the distance between the light emit part 4 and each of the light receive parts 5 and 5' is longer than half of the length of the cassette 1. Due to the longer distance between the light emit part 4 and each light receive part 5 or 5', large amount of electric current should be sent to the LED of the light emit part 4 in order for letting the part 4 emit sufficient light. In this regard, the typical checking method for tape top and tape end should be accompanied by waste of large amount of electric power and this causes a serious problem in the data recording and reproducing apparatus. Particularly, portable VCRs such as camera-integrated VCRs should be reduced in their effective filming time since substantial part of charged electric power of them is consumed for checking the tape top and tape end. Furthermore, the top-end checking LED is limited in its life span, so that the LED may be short-lived when the LED is turned on continuously for checking the tape top and tape end. In order to extend the expected life span of the LED as well as to save the energy, the LED may be repeatedly turned on and turned off at regular time intervals. However, when repeatedly turning on and turning off the LED at regular time intervals as described above, there is caused a problem in that pulse noise is generated.